Unloading valve



Jan. 25 1955 J. A. COMPTON UNLOADING VALVE Filed Aug. 24, 1949 j'i on 5g? m QC n hi6 Q 32 A] n a L 1 6 1 L n a Q in J United States Patent UNLOADING VALVE James A. Compton, South Euclid, Ohio, assignor to Borg- Warner Corporation, Chicago, Ill., a corporation of Illinois Application August 24, 1949, Serial No. 112,001

8 Claims. (Cl. 137-569) This invention relates to unloading valves, and more particularly, to a solenoid actuated type unloading valve.

It is sometimes desirable to incorporate in fluid pumping apparatus an unloading valve capable of opening very rapidly to dump the entire output of the pump. While such valves have been actuated heretofore by solenoid mechanisms, it has been found that using conventional designs, it is difiicult without resorting to excessive valve clearances to obtain very rapid action.

An object of the present invention is to provide a new and improved unloading valve, and more particularly an unloading valve actuated by a solenoid.

A further object of the present invention is to provide an unloading valve capable of extremely rapid and positive opening action.

In accordance with one embodiment of this invention, an unloading valve for a liquid pump may comprise a housing enclosing a balanced, spool type, axially shiftable valve and provision is made in the housing for bleeding apart of the high pressure output of the pump into a chamber including as one wall thereof one end wall of the spool valve. This chamber is normally vented to low pressure when the valve is closed, but upon energizing the solenoid, the venting aperture is closed and pressure building up in the chamber urges the spool valve to open position. This hydraulic pressure cooperates with the pressure applied by the solenoid plunger to provide extremely rapid opening.

Other objects and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the drawing wherein:

Fig. 1 is an axial, sectional view of a solenoid type unloading valve, constructed in accordance with one embodiment of this invention; and

Fig. 2 is a schematic view of a dual pumping system incorporating the unloading valve of Fig. 1.

Referring first to Fig. 2 of the drawings, a fluid pumping system is there shown diagrammatically in order to facilitate an understanding of the operation and the particular utility of the unloading valve of the present invention. It is to be understood, however, that this pumping system is shown only by way of example and that the unloading valve may well be incorporated in other pumping systems or associated with a different type of pressure source without departing from the scope of the invention.

As will be seen from Fig. 2, the system includes a first pump or pressure source 5 having its inlet 6 connected to a sump 7. The discharge side or outlet 8 of the pump 5 may be connected to a suitable pressure utilization device (not shown) and is also connected through line 9 to the unloading valve 10 of the present invention. Unloading valve 10 is normally closed and consequently, the entire output of the pump 5 is then supplied to the utilization device. A second or emergency pump or pressure source 11 also has its inlet 12 connected to the sump or fluid reservoir 7 and its outlet 13 may be connected to the same utilization device as that of the pump 5, suitable check and relief valves being provided where necessary as, for example, the relief valve 14 connected between the output of the emergency pump 11 and the sump 7 to dump the output of the emergency pump while the main pump 5 is functioning normally. While the elements are shown separately in Fig. 2, such a pumping system may well be incorporated in a single unitary structure, as will be readily understood by those skilled in the art.

2,700,397 Patented Jan. 25, 1955 Such a pumping system may be employed in an aircraft, for example, as the fuel pumping system or as a part of the hydraulic control system. Where so employed, it is desirable as a safety measure to be able to test the operation of the secondary system, that is, to check regularly the operability of the emergency pump which, in such an arrangement, is intended, upon failure of the main pump, to immediately supply the pressure requirements of the system. It is to provide for the making of such tests or checks that the unloading valve 10 is incorporated in the system. To provide a suitable check, it is obviously necessary that the unloading valve 10 be capable of opening very rapidly to permit bypassing substantially the entire output of the pump 5 to the inlet or sump line. The unloading valve of the present invention fully meets these requirements.

Referring now to Fig. 1, which shows the unloading valve in detail, the reference numeral 15 designates a portion of a pump body such as might enclose the pumps 5 and 11 of Fig. 2, for example, where incorporated in a unitary structure. This portion of the pump body is provided with an elongated chamber 16 of generally cylindrical configuration to receive and enclose the unloading valve designated generally at 10. The unloading valve assembly includes a'hollow, cylindrical valve housing 17 in which a balanced, spool-shaped valve 20 is slidably journalled. The normal position of the spool valve 20 is that shown, that is, the closed position in which the full output of the associated pump 5 is delivered to the utilization device. Opening of the valve is controlled through a solenoid assembly, designated at 21, the solenoid assembly being rigidly mounted on the right end of the valve housing 17, as shown. The right end portion of the valve housing 17 is peripherally threaded and threadably engages a complementarily threaded portion of the chamber 16 to seat a flanged or shouldered end portion 22, integrally formed with housing 17 at the right end thereof, on the right end of the wall of ghaimber 16, thus securing the valve housing in the pump The spool-shaped valve 20 has formed about the central portion thereof a wide, relatively deep, annular groove 23. Groove 23 defines with the adjacent wall of the valve housing 17 a pressure chamber 24 to which pressure is communicated from the bypass line 9 of the pump 5 through a plurality of radially spaced apertures 25 formed in the adjacent side wall of the valve housing 17' and communicating at their outer ends with a wide, annular recess 26 formed in the periphery of the midportion of valve housing 17. The groove 23 is made substantially wider than the side wall apertures 25 and, thus, when the valve 20 is moved to open position, as will be hereinafter described, the groove 23 still overlaps the inlet apertures, thus providing the return passage to the sump 7.

In order to prevent leakage of fluid being pumped to the right or the left of the recess 26 through the chamber 16, sealing or packing rings 27 and 28 are disposed on the right and left sides, respectively, of the recess 26. The sealing rings 27 and 28 are received in annular grooves 30 and 31, respectively, formed in the periphery of the valve housing wall adjacent either end of recess 26 and which are made of such a depth that the rings 27 and 28 are compressed between the base of the groove and the inner wall of the chamber 16 to provide a suitable seal.

The left end portion of the spool valve 20 comprises a generally conical flange 32, the right side of which defines the left end wall of the annular pressure chamber 24, and the flange 32 extends radially outwardly to the left so that the portion of the flange 32 immediately adjacent the outer periphery of the flange and on the right side thereof may seat on a valve seat 33 formed by abruptly widening the spool valve chamber at this point. Integrally formed with and extending to the left from the periphery of the flange 32 is a cylindrical or guide portion 34 of the spool valve, which portion 34 extends sufliciently to the left to be received and journalled in the left end of the valve housing 17, this left end portion of the housing having a somewhat greater internal diameter than the main portion thereof byvirtue of the widening to provide the valve seat 33. The cylindrical portion 34 of the valve 20 is journalled in the left end portion-of valve housing 17 with suflicient side and end clearance to permit freedom of movement of the valve 2,0, .while enabling the portion 34 to serve as a guide for the left end of the valve thereby to maintain axial alignment thereof with the housing.

' 1.611 the valve 20 is opened by unseating the flange 32, a passage is provided from the annular pressure chamber 24 through a pair of radially extending, circumferentially elongated apertures oryslots 35 formed in the valve housing 17 immediately to the left of valve seat 33. The outer wall of the valve housing 17 to the left of valve seat 33 is made sufiiciently less in diameter than the inner wall of the chamber 16 so that an annular passage 36 is provided from the apertures 35 to a low pressure zone, the left end of the unloading valve in the 'embodiment'illustrated in Fig. 2 being connected to the sump 7.

In order to hold the spool valve normally closed, a helically coiled spring 37 is mounted within the left end portion of the valve housing 17, the right end of the spring 3;? bearing against the left inner side of the flanged portion of the valve 20 while the left end of the spring 37 bears against an annular retainer plate 38 mounted in the left end of the valve housing, which is opeii, by split ring 40 received in an annular groove 41, formed on the inner side of the left end of the valve housing. Because the areas of the inner sides of the two ends of the spool valve 20 which are exposed to pressure from port 9 are equal, pressure in chamber 24 is exerted equally in both the right and left directions. The spring 37 is, therefore, of light weight and merely provides sufiicient force to overcome frictional and gravity forces and insure seating of the valve.

The right end portion of the spool valve 20 is centrally recessed to form a relatively deep, axially extending valve chamber 42 in which the left portion of a needle valve 43 is disposed. The right portion of the needle valve 43 is journalled in an axially extending aperture 44 formed in a generally cylindrical block or bushing 45 which is threaded into and supported by a sleeve-shaped housing member 46, in turn threaded into the right end of valve housing 17. A flange 47, integrally formed with sleeve member 46, seats against the right end wall of valve housing 17. Packing ring 48 prevents leakage between the housing 17 and member 46.

The chamber 42 and the right end of the spool valve 20 define with the left ends of bushing 45 and housing member 46 a second pressure chamber 50. By the application of suflicient pressure to this chamber 50, the. spool valve 20 may be caused to move to the left against the pressure of spring 37 to open the spool valve by unseating the flange 32 from the valve seat 33.

Pressure is supplied to the chamber 50 through a pair of oppositely, radially extending passages 51 which communicate at their inner ends with the left portion of the chamber 42 and at their outer ends with the annular pressure chamber 24 by virtue of a leakage path 52 provided between the periphery of the right portion of the valve 20 and the inner wall of the valve housing 17, by a suitable choice of their relative dimensions. That is to say, a suflicient clearance is provided between these twotadjacent surfaces to permit a definite but restricted amount of the fluid in the chamber 24 to pass into the chambers 42 and 50.

The pressure in these chambers 42 and 50 is normally vented to atmospheric or inlet pressure, when the valve 20 is closed, through an axially extending, venting aperture 53 formed in the spool valve and an aperture 54 defined by the inner periphery of the annular spring retainer plate 38, the aperture 54 communicating directly to the sump 7. However, it will be noted that the left end of needle valve 43 has a conical tip 55 adapted to seat on and close the right entrance to the venting aperture 53 formed through the spool valve 20. Needle valve 43 is, normally held in open position by a helically coiled spring 56 disposed about the periphery of theleft portion of the needle valve and having its left end bearing against the right end wall of the chamber 42 while the right end of the spring 56 bears against a flange. 57 formed about the middle of the needle valve. Thus, when the needle valve 43 seats on the right entrance to the aperture 53, venting ceases and pressure immediately builds up in the pressure chamberISO. Ordinarily, this pressure will far exceed any counterforceappli'ed bythe spring 4 37 and will effect an immediate opening of the valve 20.

Control of the operation of the needle valve 43 is effected by the solenoid assembly 21 which comprises essentially a winding 60, of the usual toroidal shape, having associated therewith leads 61 connected through plug 62 to a suitable source of power through a switch (not shown). A casing 63 encloses the solenoid assembly and is supported at its left end on the flange portion 22 of the valve housing 1'7 by an integrally formed, inwardly turned rim 64, which is sandwiched between the left wall of the flange 22 and the right end of the pump body 15, as shown. Threading the valve housing 17 into position in the pump, secures the solenoid casing rigidly in position. Inner casing member 65, concentrically disposed with respect to the casing 63 and coil 69, provides a bearing support for an axially movable solenoid core 66. The right end of the inner casing 65 is closed to prevent the core from moving too far to the right, and it will be noted that the inner casing 65 extends to the right substantially beyond the right end of coil 60. Thus, when the spool valve 20 is closed, that is, in the position shown, and the needle valve 43 is open, as shown, the core 66 is positioned at its extreme right location, that is, with its right end bearing against the right end of the casing 65. The left end of the solenoid core 66 is tapered to form a truncated cone 67 adapted to be received in a complementarily formed, generally conical recess 68 formed in the right end of the needle valve supporting bushing 45. Spring 56 at the left end of needle valve 43 urges the right end of the needle valve into contact with the flat end of the core 61. Upon energizing the solenoid coil 60, the core 66 tending to center itself with respect to the coil 60, will move to the left against the pressure of spring 56, thereby seating the conical needle valve tip 55 on the entrance to the right end of axial aperture 53. in the spool valve 20.

It will be noted that the solenoid core 66 is provided with an axially extending passage 70, which connects at its left end with a short, angularly extending passage 71 terminating at the side of the truncated tip 67. The reason for this is that because of the clearances which must be provided, Particularly between the needle valve 43 and the bushing 45, a certain amount of the fluid being pumped and present in pressure chamber 50 will leak to the right past the bushing 45 and into the chamber defined by the truncated tip 67 of the core 66 and the recessed right end of thebushing 45.. Thus, in order to permit the core 66 to move to the left, that is, in order to avoid a hydraulic block, means must be provided to permit the fluid trapped in this chamber to, escape. The passages 70. and 71 accomplish this, and as the core moves to the left, fluid trapped at the tip of the core 66 moves back to. the right end of the core and the enlarging chamber formed between the right end of the core and the right end of inner casing 65 as the core 66 moves to the left.

Initial movement of the needle valve 43 under the impetus of the solenoid core 66 closes the venting passage 53. The hydraulic pressure, that is, the pressure of'the fluid being pumped, then builds up in the pressure chamber 50 very rapidly and overcoming the force of the spring 37, shifts the spool valve 20 to the left. The force ofthe hydraulic pressure in the chamber 54 is supplemented by the force developed by the solenoid, thus providing the most rapid action possible. Since the solenoid causes the needle valve to follow the valve 20 and to remain seated on the entrance to venting aperture 53, the venting aperture is maintained closed.

Pressure above atmospheric pressure continues to be exerted on the pressure responsive end surfaces of the valve 20 even after the valve has moved to partially open position. As soon as the valve 20 moves to the left the distance comprising the length of leakage passage 52, the passages 51: are then directly connected to the pressure chamber 24'. Under these conditions, a certain minimum hydraulic pressure is maintained in pressure chamber 50, by virtue of the spool valve seating spring 37, as will be readily understood, and this pressure in combination with the force developed by. the solenoid, assures full opening of the unloading'valye.

It has been found in practice that the unloading valve of this invention is capable, in a system of the type illustrated in Fig. 2;, of reducing the main pump discharge pressure from. approximately 600 pounds persquare inch to 16 pounds per'square inch in 0.20 second or less. It

will be appreciated that this constitutes extremelyrapid operation and that this has been accomplished in accordance with this invention by a simple and efiicient structure.

Where herein the various parts of this invention have been referred to as being located in a right or a left position, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative positions of the parts as shown in the accompanying drawings.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit or scope of the present invention.

What is claimed is:

1. An unloading valve for a fluid pumping system including a valve housing, a normally closed, axially shiftable valve slidably journalled in said housing, a flange at one end of said valve and an enlarged portion at the opposite end, the space between said ends defining a first pressure chamber, said housing having an inlet aperture formed therein arranged to communicate fluid under pressure to said pressure chamber, said flange forming a closure member for said chamber, a second pressure chamber in said housing including the outer end of said enlarged portion of the valve as one wall thereof, restricted flow path means connecting said first and said second chambers, means defining a venting passage for venting said second chamber to a zone of relatively low pressure, said venting passage being normally open when said valve is in closed position, electromagnetically actuated means for closing said venting passage to increase the pressure in said chamber whereby to shift said valve to open position, said electromagnetically actuated means being arranged to supplement the opening force applied to said valve from said second pressure chamber, and means bypassing said restricted flow path means upon partial opening of said valve whereby inlet pressure is directly supplied to said second chamber to increase the opening speed of said valve.

2. An unloading valve for a fluid pumping system including an axially shiftable, spool-shaped valve in a valve housing, a balanced pressure chamber defined by a portion of said valve intermediate the ends thereof and said housing arranged to communicate with the discharge side of said fluid pumping system, one end of said valve forming a pressure responsive motive surface, a second pres sure chamber formed in said housing and including as one wall thereof the motive surface of said valve, means defining a restricted flow path connecting said first pressure chamber and said second pressure chamber, means defining a venting aperture for said second chamber for preventing accumulation of pressure in said second chamber, means for closing the venting aperture of said second chamber to increase the pressure in said chamber whereby said valve is shifted to open position, means including a solenoid operatively associated with said valve for supplementing the opening force developed in said second chamber upon the closing of said venting aperture, and means including bypass means connected to said restricted flow path means for directing pressure directly into said second pressure chamber to accelerate the opening of said valve upon partial opening thereof.

3. An unloading valve for a fluid pumping system including an axially shiftable valve in a valve housing, a balanced pressure chamber defined by a portion of said valve intermediate the ends thereof and said housing, said chamber being arranged to communicate with the discharge side of said fluid pumping system, one end of said valve forming a pressure responsive motive surface, a second pressure chamber formed in said housing and including as one wall thereof the motive surface of said valve, means defining a restricted flow path connecting said first pressure chamber and said second pressure chamber, means defining a venting aperture for said second chamber for preventing accumulation of pressure in said second chamber, means for closing the venting aperture of said second chamber to increase the pressure in said chamber whereby said valve is shifted to open position, valve opening means including a solenoid for controlling the closing of said venting aperture closing means, said solenoid being arranged upon energization to apply an additional shifting force to said valve to open said valve, and means including bypass means connected to said restricted flow path means for directing pressure directly into said second pressure chamber to accelerate the opening of said valve upon partial opening thereof.

4. An unloading valve for a fluid pumping system including an axially shiftable, normally closed valve in a valve housing, a balanced pressure chamber defined by a portion of said valve and said housing arranged to communicate With the discharge side of said fluid pumping system, a motive surface on said valve arranged upon application of fluid pressure thereto to move said valve to open position, a second pressure chamber formed in said housing and including as one wall thereof said motive surface, means defining a restricted flow path connecting said first and second chambers, means defining a venting aperture for said second chamber for preventing accumulation of pressure therein, resilient means for holding said axially shiftable valve normally in closed position, means for closing the venting aperture of said second pressure chamber to cause accumulation of pressure therein to overcome the force of said resilient means and to shift said valve to open position, a solenoid assembly for actuating said aperture closing means, said solenoid assembly being arranged to supplement the opening force applied to said valve from said second pressure chamber, and bypass means for directing pressure available to said balanced pressure chamber to said second chamber upon partial opening of said valve to accelerate the opening thereof.

S. An unloading valve for a fluid pumping system including an axially shiftable, normally closed valve in a valve housing, a balanced pressure chamber defined by a portion of said valve and said housing arranged to communicate with the discharge side of said fluid pumping system, a motive surface on said valve arranged upon application of fluid pressure thereto to move said valve to open position, a second pressure chamber formed in said housing and including as one wall thereof said motive surface, means defining a restricted flow path connecting said first and second chambers, said means including a short restricted axially extending leakage path connected with the first pressure chamber and communicating with a relatively unrestricted passage connected to said second pressure chamber, means defining a venting aperture for said second chamber for preventing accumulation of pressure therein, resilient means for holding said axially shiftable valve normally in closedposition, means for closing the venting aperture of said second pressure chamber to cause accumulation of pressure therein to overcome the force of said resilient means and to shift said valve to open posit on, said unrestricted passage being directly connected to said first pressure chamber after axial shifting of said valve the axial length of said short restricted leakage path whereby full pressure-urged opening of the valve is augmented, and a solenoid assembly for actuating said aperture closing means, said solenoid assembly being arranged to supplement the opening force applied to said valve from said second pressure chamber.

6. An unloading valve for a fluid pumping system including a valve housing, a normally closed, axially shiftable spool valve slidably journalled in said housing, a flange at one end of said spool valve defining a closure member, an enlarged portion at the opposite end of said spool valve defining a piston, the space between said ends defining a first pressure chamber, said housing having an inlet aperture arranged to communicate fluid under pressure to said first pressure chamber, a second pressure chamber including the outer end of said piston portion as one wall thereof, means defining a restricted flow path for communicating pressure in said first chamber to said second chamber, means defining a venting passage for venting said second chamber to a zone of relatively loW pressure, sald venting passage being normally open when said valve is in closed position, electromagnetically actuated means for abruptly closing said venting passage to increase the pressure in said second chamber whereby to shift said spool valve to open position, said electromagnet1cally actuated means being arranged to supplement the openlng force applied to said valve from said second pressure chamber, and conduit means located between said first and second chambers whereby upon partial openlng of said valve inlet pressure is communicated directly to said second chamber, thus operatively eliminating the function of said restricted flow path defining means and accelerating the opening of said valve.

7- In n unloadi g valve ncl din a valve h using, a first balanc d pressur cham er defined y a p rtion o said valve, and said, housing, said valve being shiftable from normally closed position to establish a flow path from said first pressure chamber to a zone of relatively low pressure, a second Pressure chamber defined by a portion of said valve and said housing, means connecting said first and second pressure chambers, means for venting said second pressure chamber to said zone of relatively low pressure, closure means for said venting means ar ranged to shift said valve to open position by increasing the pressure in said second chamber, and electromagnetically actuated means operatively associated with said closure means to close said vent means and also operatively associated with said valve for supplementing the action of pressure in said second chamber to increase the rapidity of opening of said axially shiftable valve, said means connecting said first and second pressure chambers further including a means for directing pressure from a source of high pressure to said second pressure chamber to additionally supplement the action of pressure in said second chamber upon partial opening of said axially shiftable valve whereby the rapidity of opening of said axially shiftable valve is additionally'increased.

8. In an unloading valve, a valve housing, a first balanced pressure chamber defined by a portion of said valve and said housing, said valve being shiftable from normally closed position to establish a flow path from said first pressure chamber to a Zone of relatively low pressure, a second pressure chamber defined by a portion of said valve and said housing, means connecting said first and second pressure chambers, said means including a short restricted leakage path connected with the first pressure chamber and communicating with a relatively unrestricted passage connected to said second pressure chamber, means for venting said second pressure chamber to said zone of relatively low p essure clo ure means for sai ent n m ans arranged t shitt said valve t pen po t o y creasin he p essu e in sa sec n ha er, electr ma e ca ly actuated means operatively associated with said closure me ns or clos n a d en n m s t y n a g the pressure in said second chamber, said unrestricted passge being directly connected to said first pressure chamber after axial shifting of said valve the axial length of said short restricted leakage path whereby pressure from the first pressure chamber augments the opening of the valve, said electromagnetically actuated means further being operatively associated with said valve for' supplementing the action of pressure in said second chamber tolincrease the rapidity of opening of said axially shiftable va ve.

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